drm/rockchip: remove of_match_ptr() from analogix dp driver

Kernel test robot throws below warning when CONFIG_OF
is not set.

>> drivers/gpu/drm/rockchip/analogix_dp-rockchip.c:457:34:
warning: unused variable 'rockchip_dp_dt_ids' [-Wunused-const-variable]
   static const struct of_device_id rockchip_dp_dt_ids[] = {

Fixed it by removing of_match_ptr().

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210607184836.3502-1-jrdr.linux@gmail.com